Piazza del Campo, is where you can find all the major monuments of the city. Just like Rome, this city is built on hills, so when you begin to walk in the streets of Siena, even now you know that you will find challenging climbs and descents pleasant. Of one thing you can be sure: do not get bored. In fact, the scenarios that open up before your eyes constantly change, because each of the 17 city districts has its own special treasure trove of beauty and traditions. Certainly, you will put the Cathedral of things to see. Well, remember to look carefully at the facade of the church: the statues you see are copies, to admire the originals you will need to enter the close of the Opera Metropolitan Museum. http://www.italia.it/en/home.html
Two other famous monuments of Siena are certainly on your list, because Piazza del Campo and the Public Palace are two unmissable experiences. That elegant Gothic building – completed in the year 1342 – is the town hall, and its magnificent medieval rooms (decorated by famous artists), are waiting. What you see in front of City Hall is the Loggia of the Merchandise (where merchants and bankers treated their affairs), a building designed in 1417 and completed in 1444. Looking at the bell tower of the Cathedral, you too will have noted the architectural oddity. In fact, it is an unusual thing to see that every row of arches of the bell tower, has a window in less than the order of the upper arches. http://www.aboutsiena.com/index.html
If you have time, remember to go in via the Galluzza, because it is in that way that you can find the house of Santa Caterina, a building where she was born in 1347. Finally Piazza del Campo, a large space in the shape of a shell, delimited nine sectors, symbolizing the Council of Nine (that is, who ruled the city in medieval times). From the top of Torre del Mangia, Siena is beautiful to observe, but to admire the beauty of the Fonte Gaia, better get down from the tower and go to the Piazza del Campo. Those that you will see, are only copies of the bas-reliefs sculpted by Jacopo della Quercia (the originals are in the Government Building). I am sure that, walking the streets of Siena, you too have noticed an architectural curiosity, high above your eyes. Bridges and suspended corridors, connecting opposite buildings in one way, as well as linked – in those distant years of fierce struggles towns – interests opposed to other interests. Please come to the Palio di Siena, you choose the date. http://www.ilpalio.org/palioenglish.htm